How does self-shielded FCAW achieve shielding?

• A. By external shielding gas
• B. By shielding from vaporized flux displacing air
• C. By shielding with water-cooled jackets
• D. By using inert gas plus flux

Answer: (B)

Self-shielded FCAW relies on the flux inside the wire to create the protective envelope. As the arc heats the flux, it decomposes and releases gases such as carbon dioxide and nitrogen. These gases rise around the weld pool, displacing the surrounding air and forming a blanket that shields the molten metal and arc from oxygen and nitrogen in the atmosphere. The flux also leaves a slag layer that provides additional surface protection as the weld cools. This in-situ generation of shielding gas means no external shielding gas supply is needed. External shielding gas would be used in other FCAW variants, not the self-shielded type. Water-cooled jackets don’t provide shielding, and using inert gas plus flux isn’t necessary for self-shielded welding.